1. Field of the Invention
The present invention relates to demodulators for direct sequence spread spectrum component pseudonoise (PN) codes. More particularly, the present invention relates to a demodulator for faster acquisition of component codes having a novel detecting circuit and a novel carrier tracking circuit.
2. Description of the Prior Art
Demodulator circuits for component codes are not new. Such circuits are classified in International Class H04L 9/04 and in U.S. Classes 375/I and 380/34. Circuits for generating component codes are described in our U.S. Pat. No. 4,225,935, assigned to the same assignee of the present invention. This patent and references cited therein relate primarily to the method of generating component codes and describe only generally the circuits for recovering the component codes so generated.
To provide a more thorough review of demodulator circuits of the type employed in the prior art for recovering component codes, the prior art known to exist in products supplied by the Unisys Corporation will be described in greater detail hereinafter with reference to the drawings showing the prior art demodulators in this application.
Heretofore, it was generally believed that it was necessary to search each component code of a composite code sequence utilizing non-coherent detection techniques.
The present invention provides a circuit and system which permits COHERENT detection and tracking of all of the component codes of a composite code sequence after detecting the first component code of the composite code sequence by NONCOHERENT techniques.